The decision sees the £5.5m Japan fund managed by Amanda Gold, merged into the £105m New Star Pacific growth trust run by Ian Beattie.
Meanwhile, the £7.7m North America fund run by Greg Kerr is to be merged with the £12.6m North America portfolio, a fund of funds offering managed by Mark Harris.
The mergers are set to take place on June 13, subject to approval.
Both Gold and Kerr will remain at New Star to focus on their institutional responsibilities
The decision comes following both poor uptake and underperformance of the funds, with the Japan and North America funds fourth quartile over three and five-year periods.
New Star acquired the North America and Japan funds from Edinburgh Fund Managers in 2003.
The Japan fund has returned 12.1 per cent over five years compared to a 47.1 per cent return from the IMA Japan sector over the same period. Meanwhile, the North America fund has returned 3.1 per cent compared to a 28.5 per cent return in the IMA North America sector in the same five year period.
New Star investment funds managing director Mark Skinner say: “By consolidating these small portfolios into more established funds with broader remits, New Star is seeking to improve performance for investors. Investors in these funds should be well served by Ian Beattie and Mark Harris.”